Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.55	3.541%	$175.5538	$175.55	$175.55	$175.60
Purchase #2	$226.45	12.635%	$255.062	$255.06	$255.05	$255.10
Purchase #3	$206.54	11.585%	$230.4677	$230.47	$230.45	$230.50
Purchase #4	$209.29	13.861%	$238.2997	$238.30	$238.30	$238.30
Purchase #5	$121.60	7.687%	$130.9474	$130.95	$130.95	$130.90
Purchase #6	$82.95	12.681%	$93.4689	$93.47	$93.45	$93.50
Purchase #7	$28.56	13.755%	$32.4884	$32.49	$32.50	$32.50
7 purchase totals =	$1,044.94		$1,156.2879	$1,156.29	$1,156.25	$1,156.40